Jump to content

New system install. Advice please.


Friday
 Share

Recommended Posts

Hi there

 

Having lurked around here for years while researching and planning and finally going solar I now find my silence is punishing me. I have to have 15 posts before I can download the file on Axpert settings. So here goes:

We are eskom free, gave them the middle finger 2 years ago. Steep learning curve with so much BS out there that it's like wading through treacle trying to find answers and reliable info. Our first system (Mark I) was a beginners true mashup of mistakes and our current system (Mark II) works fine, we just want the new system (Mark III) capable of dealing with the full needs of our completed house. We have been slowly working on building our house, getting the components of our new system together and now finally at the point of installing it. Problem is I am still a beginner and all this is doing my head in, I may be slightly technically minded for a female, but this is all still way beyond my current knowledge and maths ability. I have questions coming out my ears and I need help - I don't want to mess up this whole expensive pile of stuff.

 

I have the following to put together into one functional system:

Microcare 1 KW inverter (being used in our current system and def not going into our new system)

Microcare 60A charge controller (being used in our current system)

Axpert 5KW inverter (new) and remote panel

4 x 260W panels (being used in our current system)

8 x 300W panels (new)

8 x Trojan  L16REB 6v 370ah batteries (18 months old, being used in our current system)

16 x Trojan  L16REB 6v 370ah batteries (new)

 

So here are some questions I have:

1. We used 70mm cable for the batteries and connections in the current system, Hubby says 35mm will do fine for new system - is this OK?

2. I want to make 3 strings of 48V. Can I still use the batteries from my existing system together with the new batteries? If not,why not? I must say we barely sipped from the batteries as we were limited by the 1KW inverter - If we dipped below 80 - 85% of battery charge it was minimal and maybe only a couple of times through winter. We ditched the wants for needs right at the start.

3. The panels - so I figure that 3 x 300W panels in series will be ok for the volts limit for the axpert controller, so I can get 2 stings of 3 x 300W panels. Can the existing 260W panels be used at all? Can I make a string with 2 x 300W + 1 x 260W panels thus giving me 4 strings of panels? Please explain the maths here to me.

4. Please could you explain why the system needs to be grounded properly and what parts of it need to be grounded and how to do this - we are an island - no grid tie.

5. We want to use the genny when power tools need to be used and to charge the batteries if needed. Can this be done with the axpert and how do we make it so that it is not automatic and only when we want it to do this.

6. Where do I put isolator switches and fuses and what kind are they and where do I get them?

 

I have more questions, but I need 15 posts see :)

 

Thanks in advance

Friday

 

Link to comment
Share on other sites

Hi Friday, welcome.

You got my attention with ditching wants for needs. Well done!

So here are some answers I have, others guys will add a lot more.

1. We used 70mm cable for the batteries and connections in the current system, Hubby says 35mm will do fine for new system - is this OK?
Yes. Keep them short as possible and you are good to go.
Although, if you have the 70mm2 cable, re-use them?

2. I want to make 3 strings of 48V. Can I still use the batteries from my existing system together with the new batteries? If not,why not?
No, do not mix old and new. The older ones will force the new ones to age prematurely. 6 months age difference is the max suggested. 

3. The panels - so I figure that 3 x 300W panels in series will be ok for the volts limit for the axpert controller, so I can get 2 stings of 3 x 300W panels. Can the existing 260W panels be used at all?
An idea, keep the 1kw Microcare inverter and controller and smaller panel array (4 x 260w) and older battery bank in play until a)) the batts are shot after many years, b)) you can sell it for a few rands? You have it, use it.

4. Please could you explain why the system needs to be grounded properly and what parts of it need to be grounded and how to do this - we are an island - no grid tie.
Safety. Others will comment a lot more.

5. We want to use the genny when power tools need to be used and to charge the batteries if needed. Can this be done with the axpert and how do we make it so that it is not automatic and only when we want it to do this.
Yes you can. Just don't exceed the max watts, about +-4000w, on the Axpert. Make sure there is enough solar so you don't use the batts unnecessarily. Max the Axpert's MPPT array with the 310w panels - you will need more. Again, lots of info from the others on the way.

6. Where do I put isolator switches and fuses and what kind are they and where do I get them?
Isolator between panels and controller/s - to disconnect panels with ease. Can use fuses but fuses cannot be pulled under load. Certain isolators can. EDIT: I have fuses right at the panels, with isolators next to the controllers. Best of both and not expensive.
Fuses between inverter / controller and battery bank.
Isolators between inverter output and loads.

Link to comment
Share on other sites

Morning @Friday

TTT has  answered all your questions bar one

The need for grounding.

Earthing has two separate components.

 Grounding of neutral.   Initially electrical systems were ungrounded but over-voltages were a problem caused by static, surges and lightning amongst other things. The solution was to ground the system. Here is a short video to demonstrate grounded and ungrounded systems. The problem was now there was a real danger that someone's body would be a conductive pathway via the earth back to source for stray current. This only occurs in ungrounded systems once there are two faults to ground. However, the nature of an ungrounded system is that the first fault can go unnoticed. It usually arcs adding to the over voltage dilemma.

The solution was the introduction of the earth/ground wire,  a highly conductive alternate pathway for stray currents NOT to ground but to source (Eskom or generator, invertor etc.). 

Component earthing like satellite dishes, solar panels is a completely different exercise.

Here is a short video to demonstrate why we ground systems.

https://www.youtube.com/watch?v=moYfF9iK_QU

 

Here is a comprehensive discussion (1 hour and 15 minutes)

 

https://www.youtube.com/watch?v=mpgAVE4UwFw&t=8s

 

Link to comment
Share on other sites

12 hours ago, Friday said:

Can I still use the batteries from my existing system together with the new batteries? If not,why not?

Maybe. Old batteries have a higher internal resistance than new ones. That means they lift up to absorption voltage faster, but they accept less of the overall current. When you have two dissimilar strings in parallel, it means the one overcharges and the other undercharges, and both die sooner than they would have otherwise. However if you accept that this inevitable fact and you manage it, the larger capacity you enjoy might offset the earlier demise of the batteries. That is your call. I've linked this paper before where some guys tested this and came to the conclusion that it can be made to work, that it is in fact done often in the telecoms industry, but that the two things that make it fail are 1) shallow depth of discharge, and 2) the newer string will die sooner due to sulfation, that you have to accept.

One way to hack around it is to mix old and new batteries in a string in equal amounts so that all strings have the same number of new and old batteries, so if you have 24 batteries of which two thirds are new, you'd make up strings with 6 new and 2 old batteries, thereby making sure each string is roughly the same overall resistance. This only works if you have a battery balancer in there as well, and once again, your old battery will have a hard time working as hard as the new ones and in the end it will still by pushed to a premature death. I have a feeling this hack will tend to have less of a negative effect on your new batteries. This is still only advisable if the batteries don't differ too much in age.

9 hours ago, The Terrible Triplett said:

Can the existing 260W panels be used at all?

You have 6 x 300W panels and 4 x 260W panels? Keep the microcare controller and put half your panels on it.

I would love to tell you to put the one 260W string on the Axpert, and put the 300W panels on the Microcare. It's a 60A controller and it has a 150V max input voltage which will be much better suited to the larger panels.

Unfortunately 4 x 60-cell panels will be too high for the Axpert. So the two options are: 1) Leave the 4 x 260W on the microcare and put strings of 3 panels each on the Axpert, or 2) put 3 x 260W panels on the Axpert and put the rest all on the microcare.

A 300W panel usually has 72 cells, a 260W panel will likely be 60 cells. Roughly 0.6V per cell open circuit, 0.5V per cell at Vmp, so you can work it out.

Placing the smaller panels on the Axpert puts both controllers exactly in their comfortable zones (Axpert at 90V-110V, Microcare at 110V to 130V), but you'll have to drop one panel.

Link to comment
Share on other sites

Hi TTT and Chris

Thank you for the answers!!

TTT - yeah, our planning took a year - Needs and Wants - one of my little soap box subjects! ... It is something that others have asked me about often - Öoooh you're on solar, I want to go solar, how did you do it? So I tell them to take a few months and forget about panels/batteries/inverters for now and the very first exercise is to work out exactly what their power needs are and what they Need as opposed to what is just convenience. And you know what, mostly their eyes glaze over and they wander away with a bemused look in their eyes LOL

We ditched anything with an element - Gas for cooking; gas hot water geysers; no tumble dryer; no hairdryer; non-electric kettle for gas stove etc We do have a toaster, but almost never use it as I now make toast in a cast iron pan on the stove, I have a hand blender I use occasionally but mostly use a good old knife and chopping board for food prep.

We sold our old stuff and bought the defy eco chest freezer which uses 86W, a Hisense fridge which uses 75W, a samsung top loader that uses max 300W, a 700W microwave (which we still can't use on a 1 KW inverter because of start-up surge hehe), a telefunken LED TV. I think the salesman at Game thought I was touched as I hauled everything out of it's display to read the info on the back to find the most power efficient for our needs - he kept saying "what does the Mama want?"

I do laundry when the sun shines enough power into our system, and line dry everything - if you turn your clothes inside out for drying then the sun doesn't fade it (a concern I saw someone else on these forums voice).

No ironing - I fold everything as I take it from the line as opposed to dumping it into the basket. Shirts and pants go strait onto a hanger. If you do that, there is very little that "needs" ironing - for an emergency pressing I got one of those small travel irons that uses 90W, which I haven't had to use yet just by being careful nothing gets crumpled and creased. I got rid of stupid creasy clothes that wrinkle just looking at them skew.

We don't have DSTV - a total waste of money in our opinion. We stream movies on our laptops if we want to see something. We also got rid of our power hungry gaming desktops and got good enough laptops that we can also game on. My old desktop PC drew 600 - 800W when gaming, my laptop uses max 65W. We play music on our laptops too. We have a charging station for phones, tablets and tools.

It is also easier for us as it's just two of us - no kids in the mix. That being said, the grand kids come and spend their holidays with us and they are amazingly adaptable - They know that this is a "tech free" house - no phones, tablets or TV and they get to be real kids for their time here - they get dirty, they play outside, they get rained on, they play in the river, they build forts and play Hunger Games... Oh they get their "tech time", but it is a reward for imagination, working together and good attitude.

Ai, there I started on the needs and wants thing ****kicks soap-box back under the bed****

Thanks

Friday

Link to comment
Share on other sites

Hi Plonkster

Thank you for the info - it is going to take me a while to go through that paper and absorb the info. It's my hubby that says "I don't want two systems"... It's himm I have to convince not to mix the batteries.

How do I set up the microcare controller into the system? The axpert has one inbuilt and I don't know how to include the extra controller? I will check the panels today and see how they are made up and take pics of the info on them.

Thanks

Friday

Link to comment
Share on other sites

18 minutes ago, plonkster said:

... but that the two things that make it fail are 1) shallow depth of discharge, and 2) the newer string will die sooner due to sulfation, that you have to accept.

Do you mean shallow as in using a lot or shallow as in using a little - I've seen both versions of interpreting DoD - When I say 80% DoD I mean only using 20% of capacity, but I've seen others mean 80% is using 80% of capacity???

Thanks

Friday

Link to comment
Share on other sites

7 minutes ago, Friday said:

How do I set up the microcare controller into the system? The axpert has one inbuilt and I don't know how to include the extra controller? I will check the panels today and see how they are made up and take pics of the info on them.

I assume you will include a Victron BMV in your setup? Absolute must especially if you're going to be mixing batteries. Then the Microcare unit simply connects directly to the battery, or to be specific, the positive cable goes to the positive of the battery bank, and the negative cable goes to inverter side of the BMV shunt. This is exactly how the MPPT inside the Axpert is wired anyway... you just don't see it because it is inside the case :-)

Link to comment
Share on other sites

Just now, Friday said:

Do you mean shallow as in using a lot or shallow as in using a little - I've seen both versions of interpreting DoD - When I say 80% DoD I mean only using 20% of capacity, but I've seen others mean 80% is using 80% of capacity???

I mean that shallow discharges is BAD for parallel strings of dissimilar nature. The issue is thus: When you start discharging the stronger string does most of the work in the beginning, and the weaker string only joins the party later. To get the weaker string to participate at all, you must discharge to a deeper DoD. The paper I linked above outlines an experiment where both strings were taken down to 100% DoD repeatedly and they came to the conclusion that under that kind of use, you will get almost the full life out of both strings. The trouble with most RE setups is that we do shallow cycles, so your new string will do all the work and the old one will just sit there.

IE, I would not mix batteries unless they cycle to at least 50% daily.

Link to comment
Share on other sites

I have no clue how to include a battery monitor thing into the system - Victron or otherwise - I did warn you this is all way above my understanding :(

OK, thanks I get the "shallow" discharge now. Just clarifying that we were on the same definition :)

Link to comment
Share on other sites

48 minutes ago, Friday said:

And you know what, mostly their eyes glaze over and they wander away with a bemused look in their eyes LOL

Amen sister. We are kindred spirits I tell you.

But us being in the city with Eskom, I have to allow Mama's bears little (not so little anymore) special ones some freedom or else. 

40 minutes ago, Friday said:

It's my hubby that says "I don't want two sy

I can say this for my Wife taught me well ... if I say same as your hubby, she will tell me on the spot: Then ask them yourself or do what I say. :D

 

23 minutes ago, Friday said:

I have no clue how to include a battery monitor thing into the system

We refer to these devices as a must: https://www.victronenergy.com/battery-monitors/bmv-700

Link to comment
Share on other sites

28 minutes ago, Friday said:

include a battery monitor thing into the system

Ok, so basically the BMV is a two-part device. It has a shunt, which is essentially a resistor with a very low impedance, and a small round display device that can very accurately measure the voltage drop across that shunt. Now if you remember school, V = IR, and R is fixed and known for the shunt, so it can measure the current going in and out very accurately. Then it integrates this over time and comes up with an amp-hour number, and this allows it to accurately tell you how much energy is left in the battery without relying on voltage (which is terribly inaccurate).

For this to work, all current going into the battery or coming out of it must pass through the shunt. So you never connect anything directly to the negative pole of the battery, the only thing that connects to the negative pole of the battery is the shunt. Everything else connects to the other end of the shunt. If you end up with too many cables competing for space, you use a small busbar, which is essentially a length of copper with bolts attached for the affixing of cable lugs :-)

People get confused with the Axpert because the PV is connected to the "inverter" rather than the battery, as you would with other standalone chargers. Internally, however, the charge controller inside the Axpert is simply connected directly to those cables that go to the battery anyway. So connecting the old Microcare "in parallel" isn't doing anything special, and since the Axpert isn't a hybrid and doesn't do specialised SoC stuff anyway, there is no reason it even needs to know that you've done this.

Link to comment
Share on other sites

20 minutes ago, The Terrible Triplett said:

... I can say this for my Wife taught me well ... if I say same as your hubby, she will tell me on the spot: Then ask them yourself or do what I say. :D

Errrrr I just tried this and got a look and hissing sound that hinted at atomic mushrooms floating around my head.... thanks!

Link to comment
Share on other sites

11 minutes ago, plonkster said:

... For this to work, all current going into the battery or coming out of it must pass through the shunt. So you never connect anything directly to the negative pole of the battery, the only thing that connects to the negative pole of the battery is the shunt. Everything else connects to the other end of the shunt. If you end up with too many cables competing for space, you use a small busbar, which is essentially a length of copper with bolts attached for the affixing of cable lugs :-)

OK concept is there, but wiring wise, how would I do this - do you have a picture of how this would work - I'm seeing the words, but not "seeing" it in my head...

Link to comment
Share on other sites

16 minutes ago, plonkster said:

... People get confused with the Axpert because the PV is connected to the "inverter" rather than the battery, as you would with other standalone chargers. Internally, however, the charge controller inside the Axpert is simply connected directly to those cables that go to the battery anyway. So connecting the old Microcare "in parallel" isn't doing anything special, and since the Axpert isn't a hybrid and doesn't do specialised SoC stuff anyway, there is no reason it even needs to know that you've done this.

I understand the way the built in controller works in the axpert, but I dont know how to wire in an extra controller? there is my problem - how do I put in the extra controller?

Link to comment
Share on other sites

2 minutes ago, Friday said:

how do I put in the extra controller

Positive side of the controller goes to battery positive, negative goes to where the red arrow points. Exactly as it was in the old system. Don't be confused because the Axpert is "wired differently", it is not, they just hide it :-)

Link to comment
Share on other sites

13 minutes ago, Friday said:

... but I dont know how to wire in an extra controller?

Axpert inverter connects to pos and neg on batteries.

So the extra external controller connects to the same pos and neg on batteries.

Caveat you must know about, you have to program both controllers identical, or they will argue. Who charges and is it bulk or absorb or float?

It makes little difference if the system is used and both controllers go into bulk and give it all they have, it is more of an issue if the loads are light.

I know for I have had 2 different makes of controllers on same bank.

Ideally it should be identical makes and models - or try and match the settings at the very least.

Link to comment
Share on other sites

Plonkster and TTT you just blew up my monday morning brain - I am going to try drawing out how I think you mean the wiring must be and post it later and you can tell me how wrong I am lol.

Thank you so much for the help so far!! You guys are stars :)

Link to comment
Share on other sites

@Friday, just a little TTT side swipe.

You have 2 inverters, 2 controllers, 2 battery banks, 2 arrays right?

Why not split the systems seeing as you have it all.

There are loads that are purely evening, like fridges, lights and a few others. 

So, an idea is to have them run on one system, you have all the parts, and that battery bank is run until it dies. 

The other system is for heavier loads daytime, with a smaller less expensive battery bank.

That is what I did for as you, I have made the same mistake years ago and seeing as I have all the stuff, I simply split it all and save on expensive battery banks.

Link to comment
Share on other sites

He needs to get over himself or show his face here. :D

You are off grid, don't waste nothing.

Ask him: Why do we want to buy more batteries if during the evenings, the bank we have, can carry the loads for another number of years if we carefully manage it, where daytime, when we use the full potential of the solar, we use a smaller cheaper bank as a buffer for clouds and all that?

Will that not be more cost effective?

Link to comment
Share on other sites

A suggestion, to be trashed out if there is an idea to be though of:

System 1: To run all that evening loads. All 500w or less.
Microcare 1 KW inverter (being used in our current system and def not going into our new system)
Microcare 60A charge controller (being used in our current system)
4 x 260W panels (being used in our current system)
16 x Trojan L16REB 6v 370ah batteries (new)

System 2: All the heavy loads daytime, tools and all that. EDIT: hairdryer, vacuum cleaners, pumps ... you have a 5kva inverter, USE IT.
Axpert 5KW inverter (new) and remote panel
8 x 300W panels (new) - make it work or take the surplus to System 1.
8 x Trojan  L16REB 6v 370ah batteries (18 months old, being used in our current system)

 

Or another option:
Advertise the batts and panels and controller here on the forum under Classifieds, MAYBE someone has similar age bank and needs more batteries, or wants a Microcare controller or more 260w panels. 

Link to comment
Share on other sites

TBH... I'm still a little shocked that someone is downgrading from a Microcare to an Axpert... (insert mental picture of me running away from torch-and-pitchfork wielding Axpert owners).

Link to comment
Share on other sites

I thought to use the existing system as is for a separate circuit for fridges and freezers. Then use the new lot for the rest?

According to Trojan the batteries should have a life span of 14 to 17 years at 80% DoD if looked after properly. This is why I ask if the 18 month difference in age is enough to be a problem.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...